Machine tool



S. MADSEN MACHINE Too;

May 429, 1945-'.

Filed Feb. 20, 1942 2 Sh-eeflS-Sheet 1 SMH TIME

Nvmrsrronp A v Trams-)Qs May 29, 1945. 5 MADSEN l 2,376,929 MAGHINE- Tobi. l Filed Feb. 20, 1942 2 sheets-Sheet 2 Y' Patented May 29, 1945 Sern Madsen,. Rockford, Ill`. assigner Ato `Mattison Machinel Works, Rockford; lll., a corporation of Illinois' Application February 20, 1194?., Serial NoY 431.6111

7 Claims.

' This invention. relates to machine tools of the type in which the work', while being operated on, is supported on a work table of heavy rigid construction slidable back and forth'` along bed ways to present the work to a metalf removing unit. Frequently, suchreciprocation of the table is effected by hydraulic actuators including a cylinder'A disposed beneath the table.

In certain machine tools, particularly those such as grinders and planers wherein the table is actuated hydraulically or reciprocated for prolonged' intervals at a comparatively high speed'. the iiat top surface of the table becomes distorted and this distortion is suiiicient to producel objectionable inaccuraciesin the finished Work. I have discovered that such distortion is due to' a comparatively small and quite` widely variable temperature diierence produced* between the upper and lower sides of theV table by sources of heat to which the underside ofthe table is subjected. One of these sources is rubbing friction produced between, the coacting slideways" even though the latter areV lubricated adequately. AHeat is also radiated to thetable from' the hydraulic' actuator which becomes heated to a temperature depending on .the extent of `working of the pressure Huid. Coolant flowing down over the table top usually increases this temperature differential.

Based on this. discovery, the primary object of the presentA invention is to reduce and substantially eliminate.v the distortion abovereferred to.

Another object is to providemeans which is equally effective at all times in eliminating. table distortion.

A further object is to incorporate in the con,- struction of thetable itselfv asimple and. effective means for eliminating thermal distortion of the character referred to.

Still. another object is to prevent table distortion by differentiall heating through the use of means which does not. detract appreciably from the rigidity of the table' construction;

The inventionl also resides` inv the novel character of' the individualI means provided to: prevent distortion by heatI from the different sources.

Other objects and advantages,l of the. invention will become apparent fronithefollowing detailed description taken in connection with thez accom.- panyingA drawings.. in which Figure 1k is a fragmentary cross-section of a grinding machine equipped withthe present in;- venti'on, the section being along `the line' i-i of Figi 2i'.

lig'.. 2' is a fragmentary longitudinal sectional view, taken along the line2-2' of Fig. 1.

Fig. 3` is abottom'view of the work table.

Figs. 4 and 5- are sections taken respectively along.' the' lines 4-4 and 5-5f ofk Figi 3.

Fig. 6 isa fragmentary side elevation oi that.

`part of the table shown in Fig. 5.

Fig. 7 isl a. chart of temperatureY and' distortion curves. A

While the invention is susceptible of various modifications and alternative constructions, I have shown inthe drawings and will herein describe in detail the preferred embodiment. It is tobe understood, however,. that I doi not' intend to limit the invention byl such disclosure but aim to cover all modications' and' alternative constructions falling within the spirit andl scopev of the invention as expressed in the appended claims. v

As illustrativefof the type of machine inzwhch the invention. is`useul`, I have shown inthe drawings a; surface grinder comprising generally a. bed '01 ai work table I1 Iv supported on the bed for endlwisel reciprocation and a: power rotated grinding wheel I 2 mounted on'f a head l3` which may be ad?` justed. vertically tailoring the wheel into and out ci engagement with the upper surface of a work piece: clamped' on the top Hi of the table. As is common' in practice. two elongatedways l5 and |v6- formed along opposite sides of the bed receive which may be extended suitable `stationary vguards for' excluding grit andt dirt: from thel ways.

The table, which isusually a' thick-Y iron block with the ribs cast integral therewith, is positioned laterally in the present instance by making one pair et the ways of generally iff-shape'. Ii desired, the

Weight ot' the table may lb'e reduced while maintaining the proper rigidity by providing cross ribs 22 onl the underv side between the ribs t9 a-nd 20.

V Recesses' l23 inf the ibied'. interruptA the bed ways #51' and t6; and are lle'd with' lubricant which is theopposite end ofthe table.- Valve means (not shown) controlled automatically in response to Despite the eflicient lubrication of the way surl faces, `I have discovered that the rubbing friction occurring during rapid reciprocation of the table for a prolongedinterval causes the ways II and l I8 to be heated to a temperature-several'. degrees above the upper surface I4 of the table which surface is usually maintained at about room temperature by the coolant flowed thereon as above l described. As illustrated by the curve Afsu'ch 'l' differential heating develops graduallyafter the machine has been started and then becomes subcontinuous operation. 'I'he warping of the table are not as deep as the ribs as indicated by the positions of their roots 38. Preferably, the slots are formed at about two foot intervals and are about 1% of an inch wide, each extending completely across the table ways. With this construction, the intermediate rib sections 3B between two adjacent slots and the terminal sections are free to expand under the heat applied at its way surface so that any bowing of this surface that results will be confined to such section.

, Such bowing will, of course, be so extremely small ing way surfaces lled completely and avoid ex- I stantially uniform after a prolonged interval'of due to this differential alone results in raisingv of the ends of the table surface I4 above the center as shownlloy the curve B. At the same time, the hydraulic iiuid owing through the control valves andlconduits is worked 1so that the fluid and therefore thecylinders' 26 become heated as shown by the curve C.' lThis heat is yradiated to l the underside of the table and this alone produces further warping in amounts shown by the curve D, The total distortion due to the two sources of heat is shown by the curve E. 'I'he distortion Ibecomes noticeable after the machine has been in operation several rminutes and increases progressively, finally becoming somewhat stabilized after prolonged continuous reciprocation. Thus, with a machine that is' operated intermittently,Y the degree of distortion varies widely andat any particular time depends on'the temperature'r differential prevailing.

The invention contemplates the provision of means for :preventing table distortion at all times i and under all operating conditions. means functions to prevent radiation of heat i from the hydraulic cylinders to the under side of This means comprises insulation 32 Herein, one

the talble.

l filling the recesses between the ribs 22 on the I under side of the table and covering the latter.

The insulation vmay be held in place by afplate 33 secured to` the table lby, screws 34. By thus carrying the insulation on the table, the heat is not'conned in the cylinders and it is still possible to utilizey the large radiating surface of the cylinders 'as a means for dissipating heat and 'to prevent tabler distortion, it is preferred, for the sake of simplicity and reliability under all service thereby prevent excessive heating of the hydraul conditions, to :permit absorption of this heat in i the table itself and to construct the table in a novel manner such as to avoid distortion of the i top surface by the heat thus absorbed. For this purpose, the bottom portion of the table receiv- 1 ing the heat is divided longitudinally into a series 3 of sections indicated generally at 35 which sections may when heated warp or expand individul ally relative to the rigid table proper Herein, the

sections are separated longitudinally so that the waysurfaces I1 and I8 Contact the bed ways I5 and I6 over a plurality of spaced areas with the 3 face is not destroyed even though there is a temperaturey differential of several degrees.

I result that. the ilatness of the upper table sur-` l To thus divide thetable without at the same l time sacrificing the required table rigidity, the

i ribs I9 and 20 are cuttransversely to form narrow slots 31 at spaced intervals. Preferably, the'slots state.

cessive unit pressure at any point.

To minimize-the loss of pressure fed lubricantv in the slots, very small., cracks are left at the slot walls and these are of sufficient width to allow for the required expansion of the intervening rib sections 36.

With the table equipped as above described, it has Ibeen possible :to nullify the effect of the increased temperature to which the underside of the. table is subjected from various sources of heat and 4thereby eliminate distortion of the top Sur.- face I4 o-f the table or at least to reduce it to an almost unmeasurable amount as shown by the curve and this, even-.under the most unfavorable conditions off serviceuse. As a result, it is possible to form perfectly fiat surfaces on very heavy work pieces during reciprocation of the table at high speed and for prolonged intervals. I claim as my invention:v v

1. The combination of a slideway, a rigid'metal table having a way mating with said slideway and supported thereby, said table having a slot Ytherein Yextending transversely of said way to divide the portion of the tableI adjacent said way into a plurality of longitudinal sections, and a filling solidified in said slot and comprising a material. which contracts on solidifying.'

2. The combination of a slideway, a. rigid metal l table having a way mating 'with rsaid slideway and supported thereby, "said table having a slot therein extendingtransversely of said way to divide the portion ofthe table adjacent said way said slot while permitting of said independent expansion.

4. The combination of means providing a slideway, a rigid metal machine element slidable along said Vslideway'and adapted to albsorb frictional heat created at'the .coacting waysurfaces',land means dividing the way surface of said element thermal expansion of said secy and the adjacent part of the element into a plurality of separately expansible longitudinal parts while retaining the rigidityof the remainder of Y as to divide the ribs into. sections adapted for independent thermal expansion by the heat generated frictionally through the engagement of the way surfaces and the guideways during the reciprocation of the table. t

6. In a machine tool, the combination of means providing spaced parallel guideways, elongated members engageable in said guideways and slidably supported thereby, a rigid metal table in' cluding a fiat top portion and connected to said members so as to be supported thereby, each of said members being divided into longitudinal portions adapted for individual thermal expansion relative to the table whereby to nuliiiyl the eiect of differential heating between the engaged side of said members and the top of said table.

y '7. In a machine tool,` the combination of means providing spaced parallel guideways, elongated members engageable in said guideways and slidably supported thereby, a rigid metal table including a at top portion, connecting means between said members and the upper side 'onf said table supporting the latter,l and means dividing each of said members into longitudinal portions expansble individually relative to said table in vresponse to frictional heating of the members during sliding thereof along said guideways.'

' SERN MADSEN.

4 l CERTIFICATE OF CORRECTION. Patent No. 2,576,929. May 29, 19u95. SERN MADSEN.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows Page 5, second column, line 13, claim 7, for the Wordk "upper" read under; and that the Said Letters Patent shouldy be read with thiscorreetion'therein that the same may conform to the recordA of the case in the Patent Office.

Signed and sealed thiS 18th day of September, A. D. 19145.

Leslie Frazer (seal) First Assistant commissioner of Patents. 

